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ICD-10-CM 2027 diagnosis code

T36.APoisoning by, adverse effect of and underdosing of fluoroquinolone antibiotics

Not billable — use a more specific codeRequires 7th character

T36.A is a header code, so it can't be reported by itself. Choose one of the 1 more specific codes beneath it and add the required 7th character.Short description: Fluoroquinolone antibiotics

Code last changed in FY2026 (effective October 1, 2025). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About T36.A

T36.A is the ICD-10-CM diagnosis code for poisoning by, adverse effect of and underdosing of fluoroquinolone antibiotics. It belongs to category T36 (poisoning by, adverse effect of and underdosing of systemic antibiotics), block T36-T50 (poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances) and chapter 19 (injury, poisoning and certain other consequences of external causes). It is a header code, so it can't be reported by itself; one of its 1 subcodes must be used instead.

Within T36 (poisoning by, adverse effect of and underdosing of systemic antibiotics), T36.A is specifically for poisoning by, adverse effect of and underdosing of fluoroquinolone antibiotics. Related codes cover penicillins (T36.0), cephalosporins and other beta-lactam antibiotics (T36.1), chloramphenicol group (T36.2), macrolides (T36.3), tetracyclines (T36.4), aminoglycosides (T36.5), rifampicins (T36.6), antifungal antibiotics, systemically used (T36.7) and 2 more.

Codes in this range require a 7th character: A for initial encounter, D for subsequent encounter and S for sequela. Use placeholder "X" characters to fill any empty positions before the 7th character.

It was added in FY2026, effective October 1, 2025.

7th character

The appropriate 7th character is to be added to each code from category T36

  • Ainitial encounter
  • Dsubsequent encounter
  • Ssequela

Notes that apply from higher levels

Instructions written at a parent level also apply to T36.A.

› From T36 Poisoning by, adverse effect of and underdosing of systemic antibiotics
Excludes1
  • antineoplastic antibiotics (T45.1-)
  • locally applied antibiotic NEC (T49.0)
  • topically used antibiotic for ear, nose and throat (T49.6)
  • topically used antibiotic for eye (T49.5)

Broader instructions also apply from T36-T50 Poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances and Chapter 19: Injury, poisoning and certain other consequences of external causes.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2026 (effective 10/1/2025): Added
  • No changes since FY2026.

Common questions about T36.A

Is T36.A billable?

No. T36.A is a header code. Report one of its more specific subcodes instead.